Azure -VM - SMTP inbound port 25 is blocked

abhilash sundaresan 6 Reputation points
2019-12-27T07:11:58.12+00:00

Hosted Exchange server 2016 on Azure VM, and allowed Inbound Rules on port 25

( Unable to receive any emails from external )

Tested the flow from External to Azure-VM's Public IP on port 25, but its blocked

it looks Azure VM blcoked the port 25 on Public IP, The SMTP flow is already opened From Another Azure VM.

Telnet Result from External : ( Telnet PublicIP 25 : Could not open connection to the host,on port 25:Connectio failed)

Telnet result from Internal VM ( telnet servername 25) Flow is opened

Any suggestions ?

Regards,

Abhilash.

Azure Virtual Machines
Azure Virtual Machines
An Azure service that is used to provision Windows and Linux virtual machines.
6,983 questions
0 comments No comments
{count} vote

4 answers

Sort by: Most helpful
  1. Moamen Hany 1,091 Reputation points MVP
    2020-08-07T22:23:05.017+00:00

    Incoming SMTP 25 is working fine, but Outbound SMTP 25 is blocked by Microsoft Azure Article

    Microsoft Azure recommended to use any 3rd Smart host or use Microsoft 365 EOP as a smart host.

    http://www.moamenhany.com

    3 people found this answer helpful.
    0 comments No comments

  2. Heinrich Ulbricht 11 Reputation points
    2020-06-22T18:33:42.73+00:00

    I experience the same problem. Set up a Linux VM and cannot open INBOUND port 25.

    I created inbound rules for several other ports as well - those work. Only 25 fails to work. Doing nmap on this port shows:

    25/tcp closed smtp

    Any help is appreciated.

    1 person found this answer helpful.
    0 comments No comments

  3. msrini-MSFT 9,251 Reputation points Microsoft Employee
    2019-12-27T08:06:13.033+00:00

    Hi,

    Outbound request to port 25 is blocked by Azure platform. For more information, take a look at this documentation.

    Inbound traffic to port 25 is not blocked by platform. Can you make sure that you have allowed port 25 in the inbound rule of your NSG?


  4. Peter Passchier 1 Reputation point
    2022-11-28T02:23:25.413+00:00

    Not an answer, but saying I have the same issue. Allowed inbound port 25 from any source in NSG, but cannot see it on the WAN IP, but responsive on the local IP.264530-2022-11-28-09-20.png

    0 comments No comments